The invention is directed towards the field of thermal inkjet printers, particularly towards the pen maintenance thereof.
The service station in any thermal inkjet (TIJ) printer is a sub-assembly that is designed to enhance the life of TIJ pens, along with ensuring its health. This is accomplished in several ways. A rubber blade that is passed over the firing orifices, cleaning them of excess ink, periodically wipes the pens. All the pens are periodically fired into a xe2x80x9cspittoonxe2x80x9d. This happens at several intervals, most notably when the xe2x80x9cdot-countxe2x80x9d reaches a certain value. This xe2x80x9cdot-countxe2x80x9d indicates that a set of the orifices within a pen have been fired a certain number of times, while other orifices within the same pen have not. The carriage is positioned over the spittoon and all the orifices are fired. This has the effect of ensuring the reservoirs maintain the appropriate level of pressure and fluidity and all the orifices do not clog or weep. The service station has a set of xe2x80x9ccapsxe2x80x9d in it, one for each pen-head. During the times when the printer is not in use, the pens are positioned over the service station and the caps are moved to cover the firing heads. This protects the ink in the orifices from drying out during periods of non-use. The capping and wiping functions of the service station require motion in the service station with respect to the pens.
For TIJ printers having firing nozzles that are parallel to the direction of the carriage motion, the motion required for wiping and capping is parallel to the direction of the pen movement on the carriage. These TIJ printers, e.g. Lexmark, use the motion of the pens across the paper, which is driven by a dedicated motor, to mechanically move their service stations, as shown in FIG. 1. At the end of a print job, the pens move to the far right side of the printer where they hit a lever that moves the caps into place. When a new print job starts, the pens are moved to the extreme left of the printer. The start of this movement releases the capping switch and lowers the caps halfway, bringing the wipers into position. As the pens continue their motion, the orifices are wiped. After the final wiping motion is completed, the pen motion pulls the wipers into their xe2x80x98restxe2x80x99 position, out of the way of normal operation.
For TIJ printers having firing nozzles that are perpendicular to the direction of the carriage motion, e.g. Hewlett-Packard 800 and 900 series, shown in FIG. 2, all three of the pen servicing operations require applied motion. That motion is achieved by using a motor to maneuver the entire service station assembly. For multiple colors, the wiping function performed by the service station has an additional complication. The wiping function is performed parallel to the direction of the firing nozzles. If one wiper blade serviced multiple colors, when the same wiper surface area is passed over different color firing nozzles, as would happen if the wiping function is perpendicular to the direction of the firing nozzles, the ink supplies will become contaminated. The firing nozzles for each color are perpendicular to the direction of pen motion. Additionally, perpendicular TIJ printers provide an isolated space for the spittoon and move that spittoon into position. The isolation keeps the excess ink away from the other contents of the printer. FIG. 3 illustrates a prior art service station for a perpendicular TIJ printer.
There are two basic xe2x80x9cpen wipexe2x80x9d motions: wick and flicker. The squeegee blade may have any topology ranging from short and stiff to long and flexible. In the wick wipe, the squeegee blade is slowly dragged across the pen head, trying to pull some wet ink from each nozzle in an attempt to dissolve dried ink. In the flicker wipe, the blade is rapidly drawn across the orifices to wipe excess ink from the pen. The excess ink on the blade must then be removed. This is typically done by wiping the blade across a fixed plastic section found on the edge of the service station sub-assembly. Because of these different types of operations, speed control of the squeegee is required.
The present invention is a thermal inkjet printer with firing nozzles that deposit ink perpendicular to the direction of carriage motion, having two motors: paper and carriage. These motors, alone or in concert, provide the power to the drive train of the service station. Within the service station, the drive train is coupled to pen cleaning, e.g. wiper blade, and pen capping functions. The wiper blade moves across the pens in a direction that is perpendicular to the carriage motion. Through the use of gears, the wipers can be made to clean the pens at the same time that the paper is being advanced, using the same motor source. For capping, the caps are moved into place as the pens come to rest. The motion of the pens themselves could easily push a lever that pushes the caps into place.
In one embodiment, the paper motor powers the service station. A carriage motor is connected to a carriage via a gear-set and a belt-drive. The carriage moves along a guided track, propelled by the belt drive. The carriage includes one or more pens each containing dedicated firing nozzles. A paper path motor provides power to a feed roller via a first gear transmission. A paper pick-up transmission lifts the paper into position where a paper pick-up roller pulls the paper into the printer. A second gear transmission provides power to the paper pick-up transmission. The paper motor is coupled either directly or indirectly to the drive transmission within the service station.
In one embodiment, the carriage motor powers the service station. The carriage motor is connected to a carriage via a gear-set and a belt-drive. The carriage moves along a guided track, propelled by the belt drive. The carriage includes one or more pens each containing dedicated firing nozzles. A paper path motor provides power to a feed roller via a first gear transmission. A paper pick-up transmission lifts the paper into position where a paper pick-up roller pulls the paper into the printer. A second gear transmission provides power to the paper pick-up transmission. The axial motion of the carriage is transformed into perpendicular-to-axial motion for the wipers through a number of mechanical means, e.g. levers, gears, springs, or a combination thereof. The carriage motion may be used to raise and lower the pen caps also through a series of levers, gears, springs, or a combination thereof.